Lab Safety Procedures Quiz

General Lab and Safety Procedures

• Disinfect bench top with lab disinfectant upon entering the lab.
• Gather necessary materials, including lab manual and pencil, at the start.
• Wash hands with soap and water for 20 seconds when arriving and before leaving.
• Return all lab materials as directed by the instructor before exiting.
• Disinfect bench top and dry with paper towels after completing the lab.
• Push chairs under the bench to maintain a clean workspace.
• Adhere to safety rules: always wear gloves and goggles with chemicals.
• Tie hair back, do not eat or drink, maintain short nails, and wear enclosed shoes.
• Stay prepared and organized for each lab session.

Waste Disposal

• Contaminated items must be disposed of in biohazard containers.
• Non-contaminated materials can go in the regular trash bin.
• Contaminated glassware is to be placed in the sterilization area.

Aseptic Culturing Techniques

• Aseptic techniques prevent contamination of cultures and the environment by microorganisms.
• Agar is a solid growth medium made from seaweed.
• Broth is a liquid growth medium, typically used for bacterial culture.
• Inoculation transfers microbes between cultures.
• Inoculating loop and needle are essential tools used to streak bacteria or stab into solid media.

Inoculation Steps

• For broth to broth: Sterilize the loop, retrieve culture, flame the tube, and withdraw a bead of culture.
• For broth to agar slant: Same initial steps as broth to broth, with additional passing through and flaming the tube.
• For broth to agar deep: Sterilize needle, insert into tube, and withdraw after inoculation.
• Label and incubate media properly, particularly agar plates, using tape for clear identification.

Streak Plates and Pure Cultures

• Streak plates aim to isolate single bacterial cells on Petri dishes.
• Pure cultures consist of a single microbe type, achieved by isolating from a single cell.

Introduction to the Microscope

• Familiarize with all microscope parts and their functions.
• Calculate total magnification using the objective and ocular lens values.
  • 4x → 40x, 10x → 100x, 40x → 400x, 100x → 1000x.
• Key functions include magnification, resolution (detail visibility), and parfocalism (maintenance of focus).

Focusing and Specimen Viewing

• Start with the lowest magnification (4x or 10x) for initial viewing.
• Position the slide on the stage, using coarse focus to bring the specimen into view.
• Center the specimen and adjust lighting before fine-tuning focus.
• Switch to higher magnification if necessary, re-adjusting focus.

Cleaning and Storing Microscopes

• Lower the stage and rotate to 4X objective before cleaning.
• Use lens cleaner and a Q-tip for lenses, and a Kimwipe for the stage and knobs.
• Turn off the light, unplug the microscope, and wrap it carefully.
• Ensure instructor checks the stored microscope.

Staining Labs

• Simple stain: Basic dyes enhance visibility of bacterial shape and arrangement.
• Negative stain: Stains the background, leaving cells clear for structural analysis.
• Capsule stain: Identifies bacteria with protective capsules.
• Gram stain: Differentiates bacteria based on cell wall characteristics (purple for Gram positive, pink for Gram negative).
• Acid-fast stain: Identifies bacteria with waxy cell walls, visualized in red.

Contrast Between Stains

• Basic stains directly color the cells.
• Acidic stains color the background instead, leaving cells unstained.

Differential Staining Procedures

• Gram stain steps: Crystal violet, iodine, ethanol, and safranin.
• Negative stain uses nigrosine for visualization.
• Acid-fast stain steps: Carbon fuchsin, heat, iodine, acid-alcohol wash, and methylene blue.
• Endospore stain procedures: Malachite green, heat, rinse, and safranin.
• Basic stain: Crystal violet followed by water rinse.
• Capsule stain: Crystal violet and copper sulfate for visualization of encapsulated bacteria.